docs: def _process_mrk_acc_view_for_equiv(self, limit):
          """
          Add the equivalences, either sameAs or equivalentClass,
          depending on the nature of the marker.
          We only process the ENSEMBL genes and NCBI gene ids.
          :param limit:
          :return:
  
          """
          if self.test_mode:
              graph = self.testgraph
          else:
              graph = self.graph
          model = Model(graph)
          # pass through the file again,
          # and make the equivalence statements to a subset of the idspaces.
          # TODO verify the difference between what the
          # mrk_acc_view vs mrk_summary_view buys us here.
          # if nothing, then we should remove one or the other.
          LOG.info("mapping marker equivalent identifiers in mrk_acc_view")
          line_counter = 0
          with open('/'.join((self.rawdir, 'mrk_acc_view')), 'r') as f:
              f.readline()  # read the header row; skip
              for line in f:
                  line = line.rstrip("\n")
                  line_counter += 1
                  (accid, prefix_part, logicaldb_key, object_key,
                   preferred, organism_key) = line.split('\t')
  
                  if self.test_mode is True:
                      if int(object_key) not in self.test_keys.get('marker'):
                          continue
  
                  # right now not caring about other organisms
                  if organism_key != 1:
                      continue
  
                  mgiid = self.idhash['marker'].get(object_key)
                  if mgiid is None:
                      # presumably we've already added the relevant MGI ids,
                      # so skip those that we can't find
                      LOG.debug("can't find mgiid for %s", object_key)
                      continue
                  marker_id = None
                  if preferred == '1':  # TODO what does it mean if it's 0?
                      if logicaldb_key == '55':  # entrez/ncbi
                          marker_id = 'NCBIGene:' + accid
                      elif logicaldb_key == '1' and prefix_part != 'MGI:':
                          marker_id = accid
                      elif logicaldb_key == '60':
                          marker_id = 'ENSEMBL:'+accid
                      # TODO get non-preferred ids==deprecated?
  
                  if marker_id is not None:
                      if mgiid in self.markers['classes']:
                          model.addClassToGraph(marker_id, None)
                          model.addEquivalentClass(mgiid, marker_id)
                      elif mgiid in self.markers['indiv']:
                          model.addIndividualToGraph(marker_id, None)
                          model.addSameIndividual(mgiid, marker_id)
                      else:
                          LOG.error("mgiid not in class or indiv hash %s", mgiid)
  
                  if not self.test_mode and limit is not None and line_counter > limit:
                      break
  
          return